The present invention relates to a machining centre for high-precision mass production machining, but can also be applied to a precision machine tool.
More specifically, the present invention relates to an improved arrangement of the spindlehead mounting and traversing means of a machining centre or machine tool, the purpose of which is to provide greater overall rigidity and therefore obtain higher precision in mass-production machining.
The spindlehead of a precision machine tool or machining centre is currently mounted to move back and forth along a rectilinear (generally vertical) path under the control of a circulating-ball screw and nut assembly. Up to the present time, the nut of this assembly, associated with the spindle saddle, has always been kept fixed whereas the screw which passes through the saddle has been made to rotate.
Although this method is constructionally more simple in addition to being obviously more immediate, it has however the not inconsiderable drawback that the spindlehead feed force is necessarily displaced from the centre of gravity of this head by some distance (in this respect, the centre of gravity of the spindlehead lies on the spindle axis in a position corresponding with the shaft which rotates the spindle, so that it is not possible for the screw of the head traversing assembly, which passes through the head itself, to also pass through its centre of gravity) and this drawback has various negative consequences in terms of the stressing of the machine parts, their rigidity and the consequent machining precision obtainable.